1,611 research outputs found
The Journey That Saved Curious George: The True Wartime Escape of Margret and H.A. Rey
No full textMany years ago, two Jewish artists from Germany met in Brazil, started a business, fell in love, and got married. The Brazilians could not pronounce their German names, so the couple shortened them to H.A. and Margret Rey. While honeymooning in Europe, the Reys decided to stay in Paris so H.A. could pursue a career as a children\u27s book author and illustrator. During this time, H.A. started developing stories about a curious little monkey, influenced by the many monkeys he saw in Brazil. But Hitler\u27s forces delayed H.A.\u27s plans for the little monkey until he and Margret could safely escape Europe
Out and All About: Fables for Old and Young
No full textThe title-page is missing in this book, and the only reference on the web is to a reprint of a book before 1923. At least this reference gives us an author. “Routledge” appears on the spine. I read only the first fable, “The Spider and the Ants,” which lasted some 20 pages and seemed to me to lose some of its focus along the way. The book is generously illustrated with partial-page black-and-white illustrations of various sizes along the way. As the beginning T of C shows, there are here some 31 fables on 256 pages before 18 pages of advertisements. Pretty cover and spine, including gold and black on red cloth.H.A. Pag
Assessment of lime-treated clays under different environmental conditions
No full textNatural soils in work-sites are sometimes detrimental to the construction of engineering projects. Problematic soils such as soft and expansive soils are a real source of concern to the long-term stability of structures if care is not taken. Expansive soils could generate immense distress due to their volume change in response to a slight change in their water content. On the other hand, soft soils are characterised by their low shear strength and poor workability. In earthwork, replacing these soils is sometimes economically and sustainably unjustifiable in particular if they can be stabilised to improve their behaviour. Several techniques have evolved to enable construction on problematic soils such as reinforcement using fibre and planar layers and piled reinforced embankments.
Chemical treatment using, e.g. lime and/or cement is an alternative method to seize the volume change of swelling clays. The use of lime as a binding agent is becoming a popular method due to its abundant availability and cost-effectiveness. When mixed with swelling clays, lime enhances the mechanical properties, workability and reduces sensitivity to absorption and release of water. There is a consensus in the literature about the primary mechanisms, namely cation exchange, flocculation and pozzolanic reaction, which cause the changes in the soil characteristics after adding lime in the presence of water. The dispute is about whether these mechanisms occur in a sequential or synchronous manner. More precisely, the controversy concerns the formation of cementitious compounds in the pozzolanic reaction, whether it starts directly or after the cation exchange and flocculation are completed.
The current study aims to monitor the signs of the formation of such compounds using a geotechnical approach. In this context, the effect of delayed compaction, lime content, mineralogy composition, curing time and environmental temperature on the properties of lime-treated clays were investigated.
The compaction, swelling and permeability, and unconfind compression strength tests were chosen to evaluate such effect. In general, the results of the geotechnical approach have been characterised by their scattering. The sources of this dispersion are numerous and include sampling methods, pulverisation degree, mixing times and delay of compaction process, a pre-test temperature and humidity, differences in dry unit weight values, and testing methods. Therefore, in the current study, several precautions have been set to reduce the scattering in the results of such tests so that they can be used efficiently to monitor the evolution in the properties that are directly related to the formation and development of cementitious compounds. Four clays with different mineralogy compositions, covering a wide range of liquid limits, were chosen. The mechanical and hydraulic behaviour of such clays that had been treated by various concentrations of lime up to 25% at two ambient temperatures of 20 and 40oC were monitored for various curing times.
The results indicated that the timing of the onset of changes in mechanical and hydraulic properties that are related to the formation of cementitious compounds depends on the mineralogy composition of treated clay and ambient temperature. Moreover, at a given temperature, the continuity of such changes in the characteristics of a given lime-treated clay depends on the lime availability
Mechanical behaviour of fibre reinforced unsaturated clay. This investigation is to determine the improvement in the mechanical behaviour of unsaturated clayey soil after inclusion of carpet fibre waste
No full textTo acquire deeper understanding and insights into the mechanical behaviour of fibre reinforced saturated/unsaturated cohesive soils, a programme of work was designed and included. 1) Conducting standard Consolidation Undrained (CU) tests to investigate mechanical behaviour of non-reinforced fully saturated soil. 2) Studying the strength of fibre reinforced clay though unconfined compression tests. 3) Testing the behaviour of unsaturated reinforced soil in unsaturated triaxial tests. 4) Determining the soil-water characteristic curves (SWCC) on soil sample with different fibre content.
The investigation was undertaken on a clay of low plasticity index. Samples tested with addition of 1, 3 and 5 % fibre content and different values of matric suction of 50, 100 and 200 kPa, one of the challenges that were encountered in this research are how to prepare homogenous samples. A method for prepared compacted fibre reinforced soils with improved fibre distribution and density profile has been proposed and examined.
The test results indicated that waste carpet fibres increase the shear strength of unsaturated clay soils. It was also found that relative increase in strength is also a function of applied suction. An increase in waste carpet fibres was found to reduce the hysteresis of soil.
A data analysis conducted on the results of unsaturated tests as a function of fibre content and matric suction. The behaviour modelled was shown to be a perfect fit with the experimental data
Assessment of Thermally Enhanced Geo-Energy Piles and Walls
No full textGeo-energy piles and walls have long been recognized as a promising way to reduce carbon dioxide emissions while providing renewable energy. However, enhancing the thermal performance of these structures has remained a signif-icant challenge. This thesis evaluated five different approaches to improving the thermal performance of geo-energy piles and walls, through a series of experiments using a fully instrumented testing rig. The first approach involved adding graphTHERM powder to concrete to double its thermal conductivity, boosting heat transfer efficiency by an impressive 50% to 66%. The second approach tested slag-based geopolymer concrete as a sustainable construc-tion material for geo-energy piles and walls, reducing CO2 emissions by 44.5% while improving thermal performance by 14% to 21%. The third approach in-volved testing thermally enhanced soils at the geo-energy structures/soil inter-face, resulting in an 81% improvement in heat transfer efficiency. The fourth approach utilized innovative phase change material (PCM) heat exchangers that increased heat transfer efficiency by 75% and 43% in heating and cooling operations, respectively. Finally, incorporated PCM-impregnated light weight aggregates at the interface of the structure soil, significantly increasing tem-perature difference and reducing thermal deformation of geo-energy struc-tures.Overall, these innovative approaches made a significant contribution to enhancing the thermal performance of geo-energy piles and walls. However, approaches four and five, which involve utilizing PCM heat exchangers and PCM-impregnated LWA's, respectively, showed extra benefits in dropping the thermal effect on soils and reducing the thermal damage on those structures. These techniques offer great promise for improving the thermal performance of geo-energy structures
Impacts of dried Athel leaves and silica fume as eco-friendly wastes on behaviour of lime-treated heavy clay
No full textConstruction on problematic soils is challenging owing to the potential of volume changes due to
variation of moisture content. Lime stabilisation can be used to treat problematic soils. The main
drawbacks of lime addition to the clayey soils are the need for lengthy curing periods and
relatively large quantities of lime for significant improvement and also loss in ductility. Using
eco-friendly agricultural and industrial wastes, that can partially be substituted by the material
responsible for greenhouse gases such as lime, can overcome these drawbacks and decrease global
warming. In the current study, variables controlling the unconfined compressive strength of lime
treated clay with a focus on assessing the effects of moisture content were investigated.
Furthermore, the effects of adding agricultural waste (Dried Athel Leaves (DAL)) and industrial
waste (Silica Fume (SF)) on hydromechanical properties of lime treated clay were assessed. The
performance of the treated mixtures was examined based on results attained from unconfined
compressive strength, swelling pressure and permeability. Specimens were treated with deferent
percentages of lime and cured at different periods and temperatures to observe the strength
behaviour. In oedometer tests, the specimens were prepared and tested immediately after compaction.
The failure patterns were also studied to better understand the ultimate behaviour of lime
stabilised clays. The appearance and presence of cementitious products were identified by using the
scanning electron microscope and energy dispersive X-ray spectrometer techniques to elucidate their
strength development.
The findings indicated that the effect of moisture content is controlled by the clay content and
unit weight. The addition of 7% lime to clay caused a remarkable increase in the unconfined
compressive strength by 363%. The incorporation of
2% DAL and 5% SF within lime treated clay further increased the strength by 6% and 33% respectively
after curing of 28 days at 20 °c in comparison with those attained by lime treatment only. The improvement of the strength of the lime treated clay augmented with both wastes continued in long term. Temperature and lime content have positive effects on the improvement of strength, however, increasing lime content to 11% negatively affected the strength of lime treated specimens with 2% DAL. The formation of cementitious products was observed in SEM images and detected quantitatively through EDS analysis.
The results of the recorded oedometric tests for lime-DAL and lime-SF mixtures revealed that
incorporation of the 2% DAL and 5% SF reduced the clay swelling pressures by 25% and 10% compared
to that attained by lime treatment only resulting in total reductions of 93.6% and 68% from that
recorded on untreated clay. In addition, the impermeable clay transformed into permeable material
by adding DAL and SF. Of the two types of wastes considered in this research, DAL demonstrated more
superior improving capability. A further study was conducted to develop ANN model based on collated
laboratory data for the prediction of the UCS values of lime treated soils. The promising outcomes
of this research suggest that the drawbacks of lime stabilisation can be overcome by the addition
of agricultural and industrial wastes. Consequently, the findings attained could be considered in
future practice standards with regards to the requirement of lime stabilisation.Ministry of Higher Education and Scientific Research in Liby
Experimental analysis of unreinforced and reinforced piled embankment subjected to cyclic loads
No full textReinforced piled embankment technique is becoming increasingly utilised for the construction over soft grounds. Most of the studies focused on studying the behaviour of piled embankments that are loaded with static surcharge load. However, less attention has been given to the behaviour of piled embankments under cyclic loading conditions.
In this study, an experimental programme has been undertaken to improve our understanding for the behaviour of unreinforced and reinforced shallow piled embankments subject to cyclic loadings that are applied over a specific area of the embankment. The results showed that arching of the soil was adversely affected during the initial stages of cyclic loading regardless of the embankment height. However, regain of strength and recovery of the arching effect was observable during further stages of cyclic loadings. Inclusion of reinforcement layers was found to enhance the performance of load transfer mechanisms. The surface settlement increased with raising the embankment height and reduced with increasing the number of reinforcement layers.
Two preliminary experimental studies have been carried out in order to be able to understand and design the main experiment. The results showed that with increasing number of reinforcement layers, enormous cycles of loading could be applied without experiencing excessive deformation or loss of bearing resistance. Furthermore, it was observed that alternating the direction of movement significantly affected the formation of arching during the initial cycles irrespective of the embankment height.Higher Education Institute of the Libyan Governmen
Behaviour of buried pipes adjacent to ground voids under dynamic loading
No full textProtection of buried pipes is a serious issue that concerns countries around the world. Therefore, there is a need for new soil improvement techniques such as geosynthetic materials installation to protect these pipes from damage. This study used large-scale laboratory tests to study the behaviour of buried pipes. A total of 22 large-scale tests were performed to study the behaviour of buried flexible HDPE pipes with and without void presence under the protection of the geogrid reinforcing layers subjected to incrementally increasing cyclic loading.
The presence of voids located at the spring-line of the flexible buried pipes, led to a considerable increase in the soil surface settlement, pressure recorded at the pipe crown, spring-line and invert, pipe deformation and strain recorded in the pipe wall. Increasing the pipe burial depth contributed to significant reductions in the soil surface settlement, pressure recorded at the pipe crown and invert, pipe deformation and strain recorded in the pipe wall. However, the void presence limited the contribution of increasing the pipe burial depth. The inclusion of a geogrid reinforcing layer contributed to a considerable reduction in the soil surface settlement, pressure recorded at the pipe crown, spring-line and invert, pipe deformation and strain recorded in the pipe wall. The use of a combination of geogrid reinforcing layers and increasing the pipe burial depth contributed in diminishing the ground void presence effect, where better pressure distribution inside the system was achieved. Consequently, more protection was provided to the buried pipe
Dynamic soil-structure interaction of reinforced concrete buried structures under the effect of dynamic loads using soil reinforcement new technologies. Soil-structure interaction of buried rigid and flexible pipes under geogrid-reinforced soil subjected to cyclic loads
No full textRecent developments in constructions have heightened the need for protecting existing buried infrastructure. New roads and buildings may be constructed over already existing buried infrastructures e.g. buried utility pipes, leading to excessive loads threatening their stability and longevity. Additionally applied loads over water mains led to catastrophic damage, which result in severe damage to the infrastructure surrounding these mains. Therefore, providing protection to these existing buried infrastructure against increased loads due to new constructions is important and necessary.
In this research, a solution was proposed and assessed, where the protection concept would be achieved through the inclusion process of geogrid-reinforcing layers in the soil cover above the buried infrastructure. The controlling parameters for the inclusion of geogrid-reinforcing layers was assessed experimentally and numerically. Twenty-three laboratory tests were conducted on buried flexible and rigid pipes under unreinforced and geogrid-reinforced sand beds. All the investigated systems were subjected to incrementally increasing cyclic loading, where the contribution of varying the burial depth of the pipe and the number of the geogrid-reinforcing layers on the overall behaviour of the systems was investigated. To further investigate the contribution of the controlling parameters in the pipe-soil systems performance, thirty-five numerical models were performed using Abaqus software. The contribution of increasing the amplitude of the applied cyclic loading, the number of the geogrid-reinforcing layers, the burial depth of the pipe and the unit-weight of the backfill soil was investigated numerically.
The inclusion of the geogrid-reinforcing layers in the investigated pipe-soil systems had a significant influence on decreasing the transferred pressure to the crown of the pipe, generated strains along its crown, invert and spring-line, and its deformation, where reinforcing-layers sustained tensile strains. Concerning rigid pipes, the inclusion of the reinforcing-layers controlled the rebound that occurred in their invert deformation. With respect to the numerical investigation, increasing the number of the reinforcing-layers, the burial depth of the pipe and the unit-weight of the backfill soil had positive effect in decreasing the generated deformations, stresses and strains in the system, until reaching an optimum value for each parameter. Increasing the amplitude of the applied loading profile resulted in remarkable increase in the deformations, stresses and strains generated in the system. Moreover, the location of the maximum tensile strain generated in the soil was varied, as well as the reinforcing-layer, which suffered the maximum tensile strain.Government of Egyp
Efficiency of soil aquifer treatment in the removal of wastewater contaminants and endocrine disruptors. A study on the removal of triclocarban and estrogens and the effect of chemical oxygen demand and hydraulic loading rates on the reduction of organics and nutrients in the unsaturated and saturated zones of the aquifer.
No full textThis study was carried out to evaluate the performance of Soil Aquifer Treatment
(SAT) under different loading regimes, using wastewater of much higher strength
than usually encountered in SAT systems, and also to investigate the removal of the
endocrine disruptors triclocarban (TCC), estrone (E1), 17¿-estradiol (E2) and 17¿-
ethinylestradiol (EE2). SAT was simulated in the laboratory using a series of soil
columns under saturated and unsaturated conditions.
Investigation of the removal of Chemical Oxygen Demand (COD), Biochemical
Oxygen Demand (BOD), Dissolved Organic Carbon (DOC), nitrogen and phosphate
in a 2 meter long saturated soil column under a combination of constant hydraulic
loading rates (HLRs) and variable COD concentrations as well as variable HLR
under constant COD showed that at fixed HLR, a decrease in the influent
concentrations of DOC, BOD, total nitrogen and phosphate improved their removal
efficiencies. It was found that COD mass loading applied as low COD wastewater
infiltrated over short residence times would provide better effluent quality than the
same mass applied as a COD with higher concentration at long residence times. On
the other hand relatively high concentrations coupled with long residence time gave
better removal efficiency for organic nitrogen. Phosphate removal though poor under
all experimental conditions, was better at low HLRs.
In 1 meter saturated and unsaturated soil columns, E2 was the most easily removed
estrogen, while EE2 was the least removed. Reducing the thickness of the
unsaturated zone had a negative impact on removal efficiencies of the estrogens
whereas increased DOC improved the removal in the saturated columns. Better
removal efficiencies were also obtained at lower HLRs and in the presence of silt
and clay.
Sorption and biodegradation were found to be responsible for TCC removal in a 300
mm long saturated soil column, the latter mechanism however being unsustainable.
TCC removal efficiency was dependent on the applied concentration and decreased
over time and increased with column depth. Within the duration of the experimental
run, TCC negatively impacted on treatment performance, possibly due to its
antibacterial property, as evidenced by a reduction in COD removals in the column.
COD in the 2 meter column under saturated conditions was modelled successfully
with the advection dispersion equation with coupled Monod kinetics. Empirical
models were also developed for the removal of TCC and EE2 under saturated and
unsaturated conditions respectively. The empirical models predicted the TCC and
EE2 removal profiles well. There is however the need for validation of the models
developedNetherlands Organisation for International Cooperation in Higher Education (Nuffic)The Appendix files for this thesis are unavailable online via Bradford Scholars
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